Princess Margaret's 18-Year-Old Grandson (the Queen's Former Page Boy!) Shares Steamy Shirtless Selfie

This former page boy is all grown up — and royally shaking up social media with a steamy new photo.

Arthur Chatto, the 18-year-old son of Lady Sarah Chatto (the only daughter of the late Princess Margaret) and grandnephew of Queen Elizabeth II, posted a photo on his Instagram account — which was deleted and restored on Friday — showing himself in nothing but a pair of white Calvin Klein underwear, captioned "#Chatnoleg."

Much like his cousin Prince Harry, Arthur is on a military career path. He graduated earlier this year from the Combined Cadet Force at Eton and most likely will attend Edinburgh University like his older brother Samuel, 21.

The now-hunky Arthur, who is twenty-third in line for the throne, has even inspired a fan account on Instagram that tracks and celebrates his family's milestones throughout the years.

The steamy mirror selfie reveals a muscle-bound Arthur that may come as a shock to those who remember him as the regally dressed boy who carried the tail of the Queen's gowns for ceremonies, like during Prince William's 2012 knighting at the St. Giles Cathedral in Edinburgh.

The royal family is on the world's mind as the 20th anniversary of Princess Diana's tragic death approaches in August.

For full PEOPLE coverage of the 20th anniversary of Princess Diana's death:

*Pick up PEOPLE's cover story on newsstands now

*The Story of Diana, a two-part television event from PEOPLE and ABC, airs on ABC Aug. 9 and 10 at 9 p.m. E.T.

*PEOPLE's special edition Diana: Her Life and Legacy is available now

*Princess Diana: Behind the Headlines is streaming on the new People/Entertainment Weekly Network (PEN). Go to PEOPLE.com/PEN, or download the PEN app on your favorite mobile or connected TV device